#include <iostream>
#include <cmath>
#include <algorithm>
//#include <bits/stdc++.h>

using namespace std;
int jiecheng(int x)
{
	if (x>0)
		return x*jiecheng(x-1);
	else return 1;
}

int main()
{
	int x;
	cin >> x ;
	int  y = jiecheng(x);
	printf("y = %d\n",y);

	return 0; 
} 
